TypeScript · Middle · Question 73 of 75

How do you implement a type-safe event emitter?

type Events = { login: { userId: string }; logout: undefined };
on<K extends keyof Events>(event: K, cb: (payload: Events[K]) => void): void;

• ✓Correct answer: Describe events in a map type and use a generic key so the payload type follows the event name
• 2Use string events and any payloads
• 3Event emitters can't be typed